1. Field of Invention
The invention relates to a field emitting luminous device for illumination.
2. Related Art
Scientists have developed various kinds of illuminating sources using the light-emitting principles of different materials. As it is seen now, the illuminating devices have very close relations with all businesses. They have wide applications in aviation, navigation, land transportation, industries, national defense, health care, and daily life.
After the field emitting luminous mechanism was disclosed by Laboratorie d'Electronique de Technologieet d'Instrumentation (LETI) in the fourth International Vacuum Microelectronics conference, it has received very much attention from illuminator manufacturers all over the world. Its light emission principle is the same as the cathode ray tube (CRT). By bombarding electrons on a fluorescent material coated on a glass surface, the fluorescent material produces fluorescence. The advantages of the field emitting illumination are: a longer lifetime, energy-efficient, a light and thin structure, and a wide color temperature range.
The products using the field emitting illuminating mechanism are mainly the field emitting displays. The light-emitting mechanism and structure of the field emitting luminous device are very similar to those of the field emitting displays. The only difference is that each light-emitting unit (pixel) of the field emitting display has to be very small. That is, the pixels of different (or same) colors have to be so small and disposed together that they can provide the function of a display. For the field emitting luminous device, only a light-emitting layer (fluorescent powders) is required for producing light. Therefore, one can apply the structure of the field emitting display to the field emitting luminous device for making a long-lifetime and energy-efficient illuminating device.
Currently, electron amplifying devices for displays have been built. The main idea is to amplify the electrons emitted from the field emitting display by a larger factor (100˜1000) using the electron amplifying device. This helps increasing the intensity of light emitted by the field emitting display.
Please refer to FIG. 1 for the field emitting display disclosed in the U.S. Pat. No. 5,982,082. The display device is comprised of a transparent panel 38, an electrode 42, a first barrier 54, a fluorescent material 40, a separator 44, a second barrier 52, an electron amplifying layer 50, an electrode 46, space 51, and a cathode electron emitting unit 36.
The electrons 33 emitted from the cathode electron emitting unit 36 spread out in the space 51. Afterwards, the electrons 33 hit the electron amplifying layer 50 and collide with other electrons in the electron amplifying layer 50, producing secondary electrons. The secondary electrons then bombard the fluorescent material 40 to produce fluorescence, which penetrates through the panel 38 and becomes a beam 31 traveling outward.
There is only one electron amplifying layer 50 in the field emitting display device. Therefore, its amplifying effect is limited. Moreover, the space 51 has to be enclosed by separating devices. The space is thus susceptible to pressures and has a complicated structure. Consequently, it is not suitable for large-size displays.
The segmented cold cathode display panel disclosed in the U.S. Pat. No. 5,751,109 is schematically shown in FIG. 2. The electron amplifying structure is a channel plate 33, which contains an outgoing surface 62 and an incoming surface 60. The potential of the outgoing surface 62 is higher than that of the incoming surface 60 by about 1000V. In other words, the channel plate 33 is a resistor plate and the channel 41 has a potential gradient. Through the potential gradient, the electrons can be accelerated in the channel 41 and collide to produce secondary electrons.
However, the drawback of this method is that even when no electrons pass by, there is a very large potential difference between the outgoing surface 62 and the incoming surface 60 due to the existence of a finite resistance on the channel plate 33. This produces a static power consumption, P=V2/R. Moreover, such an electron amplifying structure is not feasible in products that require high precisions.